Complex nitrogen cycling in the sponge Geodia barretti

Marine sponges constitute major parts of coral reefs and deep‐water communities. They often harbour high amounts of phylogenetically and physiologically diverse microbes, which are so far poorly characterized. Many of these sponges regulate their internal oxygen concentration by modulating their ventilation behaviour providing a suitable habitat for both aerobic and anaerobic microbes. In the present study, both aerobic (nitrification) and anaerobic (denitrification, anammox) microbial processes of the nitrogen cycle were quantified in the sponge Geodia barretti and possible involved microbes were identified by molecular techniques. Nitrification rates of 566 nmol N cm^?3 sponge day^?1 were obtained when monitoring the production of nitrite and nitrate. In support of this finding, ammonia‐oxidizing Archaea (crenarchaeotes) were found by amplification of the amoA gene, and nitrite‐oxidizing bacteria of the genus Nitrospira were detected based on rRNA gene analyses. Incubation experiments with stable isotopes (¹⁵NO₃^‐ and ¹⁵NH₄⁺) revealed denitrification and anaerobic ammonium oxidation (anammox) rates of 92 nmol N cm^?3 sponge day^?1 and 3 nmol N cm^?3 sponge day^?1 respectively. Accordingly, sequences closely related to ‘Candidatus Scalindua sorokinii’ and ‘Candidatus Scalindua brodae’ were detected in 16S rRNA gene libraries. The amplification of the nirS gene revealed the presence of denitrifiers, likely belonging to the Betaproteobacteria. This is the first proof of anammox and denitrification in the same animal host, and the first proof of anammox and denitrification in sponges. The close and complex interactions of aerobic, anaerobic, autotrophic and heterotrophic microbial processes are fuelled by metabolic waste products of the sponge host, and enable efficient utilization and recirculation of nutrients within the sponge–microbe system. Since denitrification and anammox remove inorganic nitrogen from the environment, sponges may function as so far unrecognized nitrogen sinks in the ocean. In certain marine environments with high sponge cover, sponge‐mediated nitrogen mineralization processes might even be more important than sediment processes.     

Recombinant protein expression by targeting pre-selected chromosomal loci

Background  

Recombinant protein expression in mammalian cells is mostly achieved by stable integration of transgenes into the chromosomal DNA of established cell lines. The chromosomal surroundings have strong influences on the expression of transgenes. The exploitation of defined loci by targeting expression constructs with different regulatory elements is an approach to design high level expression systems. Further, this allows to evaluate the impact of chromosomal surroundings on distinct vector constructs.     

Microbial communities and activities in alpine and subalpine soils

Soil samples were collected along two slopes (south and north) at subalpine (1500–1900 m, under closed vegetation, up to the forest line) and alpine altitudes (2300–2530, under scattered vegetation, above the forest line) in the Grossglockner mountain area (Austrian central Alps). Soils were analyzed for a number of properties, including physical and chemical soil properties, microbial activity and microbial communities that were investigated using culture-dependent (viable heterotrophic bacteria) and culture-independent methods (phospholipid fatty acid analysis, FISH). Alpine soils were characterized by significantly ( P <0.01) colder climate conditions, i.e. lower mean annual air and soil temperatures, more frost and ice days and higher precipitation, compared with subalpine soils. Microbial activity (soil dehydrogenase activity) decreased with altitude; however, dehydrogenase activity was better adapted to cold in alpine soils compared with subalpine soils, as shown by the lower apparent optimum temperature for activity (30 vs. 37 °C) and the significantly ( P <0.01–0.001) higher relative activity in the low-temperature range. With increasing altitude, i.e. in alpine soils, a significant ( P <0.05–0.01) increase in the relative amount of culturable psychrophilic heterotrophic bacteria, in the relative amount of the fungal population and in the relative amount of Gram-negative bacteria was found, which indicates shifts in microbial community composition with altitude.     

Combined MRI–PET dissects dynamic changes in plant structures and functions

Unravelling the factors determining the allocation of carbon to various plant organs is one of the great challenges of modern plant biology. Studying allocation under close to natural conditions requires non-invasive methods, which are now becoming available for measuring plants on a par with those developed for humans. By combining magnetic resonance imaging (MRI) and positron emission tomography (PET), we investigated three contrasting root/shoot systems growing in sand or soil, with respect to their structures, transport routes and the translocation dynamics of recently fixed photoassimilates labelled with the short-lived radioactive carbon isotope ¹¹C. Storage organs of sugar beet ( Beta vulgaris ) and radish plants ( Raphanus sativus ) were assessed using MRI, providing images of the internal structures of the organs with high spatial resolution, and while species-specific transport sectoralities, properties of assimilate allocation and unloading characteristics were measured using PET. Growth and carbon allocation within complex root systems were monitored in maize plants ( Zea mays ), and the results may be used to identify factors affecting root growth in natural substrates or in competition with roots of other plants. MRI–PET co-registration opens the door for non-invasive analysis of plant structures and transport processes that may change in response to genomic, developmental or environmental challenges. It is our aim to make the methods applicable for quantitative analyses of plant traits in phenotyping as well as in understanding the dynamics of key processes that are essential to plant performance.     

Expression of antiapoptotic protein survivin in malignant melanoma

We examined the expression of potential tumor marker survivin by immunohistochemical staining using antisurvivin antibody (DAKO, Clone 12C4) in a panel of 25 malignant melanomas. In each section, we assessed the percentage of positively stained tumor cells, the intensity of staining and its subcellular localization. Survivin was present in 23 out of 25 cases (92%). Nuclear staining was found in 2 of these 23 cases (8.7%) only, while cytoplasmic staining only was seen in 3 of them (13%). The combined nuclear as well as cytoplasmic localization of survivin was demonstrated in 18 out of 23 cases (78.3%). In 2 cases revealing nuclear staining only, the worse histological features were more pronounced than in 3 cases with cytoplasmic staining only. Our results suggest that nuclear positivity of survivin may correlate with the degree of malignancy. In addition, we conclude that overexpression of survivin involved in the pathogenesis of melanoma represents an important diagnostic marker.